Salvage – This technique is usually feasible only when a
relatively large volume of wood is available. Prompt action in salvaging large
infestations is often necessary to prevent beetle expansion and to realize the best
possible return from the sale of infested trees. Any trees containing beetle broods
in salvage operations should be removed from the site before beetles emerge.

Cut and Leave – This course of action is best suited for
large timber stands because the resulting downed trees prevent or inhibit further
immediate utilization of the land. Attacked trees and a border of healthy trees are
felled toward the center of the spot. High temperatures on the top of the trees,
increased humidity on the bottom, and increased predation from other forest insects
and animals, may combine with disruption of emergence and attack patterns (time and
distance) to make this an alternative for beetle control. Results of recent
research are ambiguous as to the efficacy of this technique.

Pile and Burn – This may be a viable option for small
infestations in rural areas. The trees are felled in the same manner as for the cut
and leave or salvage techniques. Heavy equipment is often necessary to pile trees
together so they can be burned. These direct control techniques are described in
detail by Swain and Remion (1981).

Chemical Application – Chemicals will protect healthy trees
and/or kill broods of beetles within infested trees if they are used properly. The
cost of spraying is often small when weighed against the value
placed on the tree, the cost of tree removal, or potential damage
of expanded beetle infestations. If chemical control is selected,
the most cost-effective control can be realized only by correct
identification of the beetle
species involved, careful selection of trees to be treated, and
correct application of the insecticides.

The following procedural guide will help you select chemicals, techniques and equipment to maximize benefits from
chemical control while minimizing detrimental effects.

Selection of Chemicals
– There are currently 3 insecticides registered for control of bark beetles on
southern pines. These are lindane, chlorpyrifos (Dursban 4E) and fenitrothion
(Sumithion 8E) . Landowners may purchase lindane for their own use without an
applicator's license. Although Dursban 4E and Sumithion 8E are not restricted use
pesticides and a pesticide applicator's license is not required to purchase or use
them; they bear labeling that limits their use to professional applicators. There
is no such limitation on the use of lindane. The selection of chemicals will
usually be dictated by their effectiveness, safety and relative costs for each
application. Chemicals selected for preventive control may be less desirable for
remedial control than other compounds.

- Preventive Control -

For economic preventive control a chemical should be selected which
will prevent attacks for relatively long periods (3-12 months). If prevention is
deemed
necessary for a relatively short period, for instance 2-3 months in
the fall before low temperatures terminate beetle activity, then
selection of a chemical with a shorter residual life may save money
and reduce nontarget
contamination. For preventive control, lindane will protect pines
for up to 12 months from SPB and Ips
beetles (Berisford and Brady, 1976; Brady et al., 1980; Berisford
et al., 1981a). Chlorpyrifos and fenitrothion can provide
protection from SPB for about 3 months (Brady et al., 1980;
Berisford, et al., 1981a) and presumably can provide similar
protection from
Ips spp. Lindane can usually prevent BTB infestation for one
growing season whereas such information on Dursban and Sumithion is
not yet available.

- Remedial Control -

Chemicals for remedial control are not required to have long
residual. Since they are designed to kill beetles and brood developing within a
tree, 2-3 weeks residual is usually all that is necessary. Lindane, chlorpyrifos
and
fenitrothion all provide good remedial control of SPB and
Ips
spp. although chlorpyrifos and fenitrothion appear to be slightly
better (Berisford et al., 1981b). These compounds also break down
faster in the environment than lindane. The BTB is difficult to
control in a remedial situation because it attacks at the base of
the trees, frequently very large ones, where they are protected by
very thick bark. Lindane appears to be somewhat better than either
of the other compounds in this case. Efficacy of lindane is
increased by using a fuel oil carrier instead of water. However,
stressed trees or thin-barked trees may be damaged by the oil.

- Cost of Control -

Costs of bark beetle control obviously are an important factor in
deciding what chemical to use. In fact, costs may determine if any chemicals will
be used.
When determining relative costs, several factors should be kept in
mind.

Costs of different chemical concentrates per gallon etc. may be deceiving since concentrations may vary substantially. Be sure you know
what you are buying.

The recommended concentrations for chemicals are often different for remedial vs. preventive control. Actual costs per tree vary according to the beetle species involved, whether trees
are standing or felled, and obviously the size of the trees. Costs for BTB control are lowest since only the basal portion of trees need be treated for either remedial or preventive control. Remedial control for SPB and
Ips
beetles is most economical if trees are felled first since there is little overspray or drift. However, felling and turning costs may represent additional expense unless trees are to be cut anyway. Spraying standing trees for SPB and/or
Ips
spp. is the most expensive operation. Trees must be treated well
into the live crown resulting in some overspray and drift due to
the high pressures required and the difficulty in keeping the
spray stream on the tree at all times.

- Relative Risks to
Applicators and Non-Target Areas -

All of the chemicals registered for bark beetles of southern pines
are toxic to other organisms including humans. Some are more
toxic than others, depending on how and when they are contacted,
i.e. whether they are swallowed (oral toxicity) or are only in
contact with the skin (dermal toxicity). The toxicity of all
compounds must be established before
they can be registered for use. The terminology for determining
toxicity is standardized so one may easily compare relative
toxicities of selected chemicals. Table 1 shows the relative oral
and dermal toxicities of
lindane, chlorpyrifos and fenitrothion. Toxicity is reported as the
LD50 which is the amount of a compound that constitutes
a lethal dose for 50 percent of a test population. The
LD50
is expressed in milligrams (mg) of compound per kilogram (kg) of
body weight of the animal receiving the dose. Therefore, chemicals
with the lowest LD50s are the most toxic. These figures
vary with the
species of test animal and are based on tests with pure samples and
not the diluted formulations available for purchase.

Once insecticide sprays have dried on trees, they represent little
risk to humans or other
mammals (Berisford et. al., 1981c). However, in the process of
spraying for bark beetles, nontarget organisms may be adversely
affected. Care must be taken to minimize nontarget contamination to
insure that pets, beneficial
insects such as bees, water supplies and fish are not adversely
affected. Do not spray under windy conditions or near lakes or
streams.
When near edible crops, do not spray more than necessary to wet the bark as
excessive spray only runs off.

Certain ornamental plants may be damaged by insecticides so you should minimize
drift.